1. Field of the Invention
The present invention relates to a shift device with a synchronizer adapted for a transmission in which a pushing force applied to a sleeve can be amplified into a large pushing force acting on a synchronizer ring while gears of the transmission are shifted, thereby reducing the effort required by a driver or an actuator.
2. Description of the Related Art
A conventional shift device with a synchronizer adapted for a transmission is disclosed in U.S. Pat. No. 2,410,511. This conventional shift device includes a hub with a slanted surface and a synchronizer ring with a slanted surface, where the slanted surfaces change a part of the friction torque caused between the synchronizer ring and the hub into thrust acting on the synchronizer ring, thereby increasing synchronizing ability.
This shift device has a disadvantage in that a drag friction force is promoted between the synchronizer ring and a gear even when the sleeve is positioned at a neutral position, and not engaging with splines of the gear, because the slanted surfaces of the hub and the synchronizer ring are always contactable with each other, even at the neutral position to generate and promote thrust that pushes the synchronizer ring toward the gear.
The increase in the drag friction torque degenerates the fuel consumption of an engine, and additionally produces an increase in the oil temperature of a transmission.
In order to avoid such a problem, a shift device disclosed in EP 0 743 466 is constructed to always apply pullback force to the synchronizer so that it can move off from the gear.
This conventional shift device with the synchronizer, however, encounters a problem in that it requires a lot of parts and its assembly becomes complex, thereby increasing its manufacturing costs.